The water authority, Te Tatou Vai, said some intakes around the island have reached critical levels.
The agency in a statement says unless there is significant rain in the next fortnight, some intakes may run out and water restrictions will have to be introduced.
The Cook Islands Meteorological Service said no significant rain is forecast for the coming weeks.
Rarotonga has only recorded 44mm so far in December, which is meant to mark the start of the rainy season. Tags: